Process for simultaneously preparing pyrophoric metals and furane



L. M ESZAROS Oct. 11, 1966 PROCESS FOR SIMULTANEOUSLY PREPARING PYROPHORIC METALS AND FURANE Filed Jan. 20, 1964 INV EN TOR.

Midas MEJZflAOJ United States Patent 3,278,296 PROCESS FOR SIMULTANEOUSLY PREPARING PYROPHORIC METALS AND FURANE Lajos Mszaros, Szeged, Hungary, assignor to Chemolimpex Magyar Vegyiaru Kulkereskedelrni Vallalat Filed Jan. 20, 1964, Ser. No. 338,757 2 Claims. (Cl. 75-62) This invention relates to a process and equipment for simultaneously preparing pyrophoric metals and furane.

Several methods are known for preparing pyrophoric metals. The most generally known method consists in thermally decomposing the tartarate salts of the corresponding metals. A common disadvantage of the processes known hitherto consists in the fact that they are very expensive, and therefore none of the known processes has been practiced industrially.

Several methods are known also for the preparation of furane. For this purpose generally reductive methods are used but these processes are, mainly due to the short life of the catalyst, very expensive. Also oxidative methods are known which give furane by oxidizing the starting materials with gases containing oxygen. The disadvantage of these oxidative methods is, however, that the presence of the oxygen gas results in resinification to a certain degree.

The purpose of the invention is to eliminate the disadvantages of the processes known hitherto and to render possible the simple and cheap preparation of pyrophoric metals and furane in a single step and with good yields.

The invention is based on the recognition that metal oxides capable of being reduced to pure metal in the presence of furfural or furfuryl alcohol at temperatures not exceeding the decomposition temperature of furane, may be transformed to pyrophoric metals by the aid of furfural or furfuryl alcohol, with the simultaneous formation of furane.

The invention is a process for preparing pyrophoric metals and furane, in which furfural or furfuryl alcohol in a dry state or mixed with water is reacted at temperatures ranging from 250 to 550 C. with metal oxides capable of being reduced in the presence of furfural or furfuryl alcohol to pure metals at temperatures ranging from 250 to 55 0 C. whereby pyrophoric metal and gases containing furane are obtained, whereafter the furane is recovered from the gases in a known way. It is advantageous to use a temperature 5-20" C. lower than the melting point of the metal being formed from the metal oxide.

During this chemical reaction, the furfural or furfuryl alcohol is oxidized by the metal oxide to furane carbonic acid which, due to thermal decomposition, is transformed to furane, with the simultaneous formation of carbon dioxide and with the simultaneous reduction of the metal oxide to pyrophoric metal.

The oxygen necessary to the oxidative decomposition of the furfural or furfuryl alcohol is furnished by the oxygen being evolved during the reduction of the metal oxide.

In compliance with the process according to the invention, the pyrophoric metal obtained may be used for preparing further amounts of furane as well; in this case it is preferable to regenerate the pyrophoric metal to metal oxide at a temperature not exceeding the melting point of the metal, preferably by oxidizing with air.

A considerable amount of heat is evolved during both the furane-producing and the possible metal-oxide regenerating periods. This heat evolution may lead to the melting of the metal and thereby to the decrease of its specific surface which, on the other hand, would cause a decrease in the ability of the metal to be regenerated to 3,278,296 Patented Oct. 11, 1966 metal oxide. Therefore it is advisable to control the rate of feeding of the reaction components so that no local overheating appears and to carry out the regeneration of the pyrophoric metal to metal oxide after admixing additive agents, such as titanium dioxide, aluminum oxide and kaolin, in powder form. In this way the sintering of the pyrophoric metal during the regeneration process may be completely prevented.

After cooling in an inert gas, the pyrophoric metal being formed during the reaction may be immediately used, while the obtained furane has to be purified of contaminating substances, primarily the carbon dioxide and the possible cracking products contained in the gaseous end-product. The purification of the furane may be favorably carried out with the aid of adsorption or absorption, or by simultaneously using pressure and cooling, or possibly, after allowing the carbon dioxide to be absorbed in lye, by cooling.

If the pyrophoric metal is not immediately used, it is stored in a known way, e.g., in vacuo or in an inert gas atmosphere, or in an inert liquid, or chilled into an inert material, such as paraflin.

It is advisable to recirculate the unreacted furfural or furfuryl alcohol to the reaction space until it is fully reacted. In this way the total amount of the furfural or furfuryl alcohol is utilized.

In compliance with the process according to the invention, it is preferable to use zinc oxide, cadmium oxide, lead oxide, tin oxide, bismuth oxide or a mixture thereof as the metal oxide capable of being reduced to pure metal in the presence of furfural or furfuryl alcohol at temperatures ranging from 250 to 550 C.

The process according to the invention may be advantageously carried out in a tray reactor filled with the metal oxide to be transformed to pyrophoric metal. Before feeding into the reactor, it is advisable to pelletize the metal oxide together with the above-mentioned inert materials, such as titanium dioxide, aluminum oxide and kaolin. This pelletization may be preferably carried out by blending the metal oxide with the inert material in a ball mill, and after adding water, pressing the mixture to bodies of the desired form. By this method local overheating as well as the cracking of the organic substances may be fully eliminated.

The purity of the products obtained by the process according to the invention is equal to the purity of the starting materials. Thus e.g. if chemically pure lead oxide and furfural are used, then chemically pure pyrophoric lead and likewise chemically pure furane are obtained. Chemically pure furane may be obtained even from technically pure lead oxide if the obtained end gases are adsorbed on active charcoal and thereafter the adsorbed furane is desorbed by steam and condensed at a temperature of about 0 C.

An advantageous executional form of the equipment for carrying out the process according to the invention is illustrated by the annexed drawing.

The reactor 1 provided with electric heating and thermal insulation is filled with the metal oxide used as the oxidizing agent. The furfural or furfuryl alcohol is fed into the reactor 1 from the evaporator 2, made of metal and provided with an electric heater (not shown), through a three-way cock 3, under the influence of its own vapor pressure. The furfural or furfuryl alcohol may be fed into the evaporator 2 through the tube 4 directly or by steam distillation. For this purpose the steam may be fed into the steam-distilling vessel 6 through tube 5. The three-Way cock 3 renders possible to feed into the reactor 1 the furfural and furfuryl alcohol, respectively, or the air necessary to regenerate the pyrophoric metal to metal oxide. After leaving the reactor 1, the reaction mixture passes through the coolers 7, 8 and 9. The condensed part of the reaction mixture enters the measuring cylinder 10, where the furfural or furfuryl alcohol having a higher specific gravity forms the lower phase, and the water the upper phase. Either of these two phases may be lead through the three-way cock 11 either into the steamdistilling vessel 6 or into the outer atmosphere. The furfural or furfuryl alcohol are retrieved from the graduated burette 13. The recovered furfural or furfuryl alcohol is passed into the steam-distilling vessel 6 and thence into evaporator 2. The gases containing furane are led through the cock 12 into the adsorbing tower 14 where the furane is adsorbed on activated charcoal.

The obtained pyrophoric metal may be quickly regenerated to metal oxide by passing air from the tube 15 through the reactor 1, and thus the cycle for producing furane may be repeated. The life of the system metaloxidemetal is practically infinite.

By means of the process according to the invention, furane may be prepared both from water containing several tenths of one percent of furfural and from 100% pure furfural. In this way also waste water containing only a slight amount of furfural may be utilized for preparing furane, carbon dioxide and pyrophoric metals.

The pyrophoric metals prepared by means of the process according to the invention, particularly the pyrophoric lead, react .with alkyl and aryl halides in a way similar to the Wiirtz synthesis, with the simultaneous formation of the corresponding metal halide. Thus with the aid of the pyrophoric metals prepared by the process according to the invention, various organic syntheses may be carried out, in which metallic sodium is replaced by the pyrophoric metal. The chemical properties of the pyrophoric metals are different from those of sodium metal; consequently, the field of employment of the Wiirtz synthesis may be extended. Thus, e.g. by the aid of the chemical reaction of the pyrophoric lead, in the liquid phase diphenyl ethane may be prepared from benzyl chloride and dibenzoyl may be prepared from benzoyl chloride. Consequently, the pyrophoric metal, particularly the pyrophoric lead, may form an essential component of syntheses both in laboratories and in bulk production.

The process according to the invention may be further illustrated by the following examples.

Example 1 1000 g. of furfural are fed into the evaporator 2. The heating temperature is controlled by a toroidal transformer so that the 1000 g. of furtural are passed in 3 hours through the reactor 1 of 1.5 m, length and 50 mm. diameter and filled with minimum (red lead oxide). The end gases are cooled in the coolers 7, 8 and 9, and the condensed part of the reaction mixture enters the cylinder 10. The gases are passed through the cock 12 into the tower 14 containing activated charcoal where the furane is adsorbed while the other gases leave the tower through a gas meter. From the cylinder 10 the furfural is fed into the steam-distilling vessel 6, whence by the aid of steam fed through tube 5, it is distilled into the evaporator 2.

In this way, 400 g. of furane are obtained from the tower 14.

For producing further amounts of furane, the pyrophoric lead content of the reactor obtained as a result of the reaction is regenerated by passing air through the reactor from the tube 15 and thereby oxidizing the pyrophoric lead to minimum. The excess air leaves the system through the cooler 7. Thereafter the production of furane may be again started, and these cycles may be repeated at will. If the obtained pyrophoric lead is used as such, then, for producing further amounts of furane, the reactor has to be filled with a new charge of minimum.

Example 2 One proceeds as described in Example 1, with the difference that, instead of furfural 1000 g. of furfuryl alcohol are used. The amount of the furane obtained is likewise 400 g.

Example 3 One proceeds as described in Example 1 or 2, but the reactor is filled, instead of minimum, with cadmium oxide. The amount of the obtained furane is equivalent to that obtained in Examples 1 and 2.

Example 4 For producing pyrophoric lead, one proceeds as described in Example 1, but instead of 1000 g. of furfural, 1165 g. of furfural are passed through the reactor filled with minimum. This quantity of furfural is sufi'icient for transforming the minimum to pyrophoric lead with a yield of 100%. The obtained pyrophoric lead is cooled in nitrogen atmosphere, and it is stored after chilling into paratfin.

What I claim is:

1. A process for imultaneously preparing pyrophoric metal and furane, comprising reacting a compound selected from the class consisting of furfural and furfuryl alcohol in vapor phase at a temperature from about 250 to about 550 C. under anhydrous conditions with a metal oxide selected from the class consisting of zinc oxide, cadmium oxide, lead oxide, tin oxide, bismuth oxide and mixtures thereof thereby to obtain reaction products consisting essentially of furane, carbon dioxide and pyrophoric metal.

2. A process as claimed in claim 1, and regenerating the obtained pyrophoric metal to the corresponding metal oxide by oxidation with an oxidizing gas at a temperature not exceeding the melting point of the metal.

References Cited by the Examiner UNITED STATES PATENTS 1,915,788 1/1931 Hardy 0.5 2,174,559 10/1939 Anderson et al. 266l9 2,374,149 4/1945 Whitman 260-3461 3,005,698 10/1961 Tao 750.5 3,007,941 11/1961 Copelin et al 260-3461 3,045,995 7/1962 Handwerk 26619 FOREIGN PATENTS 510,949 8/ 1939 Great Britain. 575.362 2/1946 Great Britain.

DAVID L. RECK, Primary Examiner.

H. N. TARRING, Assistant Examiner. 

1. A PROCESS FOR SIMULTANEOUSLY PREPARING PYROPHORIC METAL AND FURANE, COMPRISING REACTING A COMPOUND SELECTED FROM THE CLASS CONSISTING OF FURFURAL AND FURFURYL ALCOHOL IN VAPOR PHASE AT A TEMPERATURE FROM ABOUT 250* TO ABOUT 550*C. UNDER ANHYDROUS CONDITIONS WITH A METAL OXIDE SELECTED FROM THE CLASS CONSISTING OF ZINC OXIDE, CADMIUM OXIDE, LEAD OXIDE, TIN OXIDE, BISMUTH OXIDE AND MIXTURES THEREOF THEREBY TO OBTAIN REACTION PRODUCTS CONSISTING ESSENTIALLY OF FURNANE, CARBON DIOXIDE AND PYROPHORIC METAL. 